I reviewed this, and I'm familiar with wlan device disappear (BCM43142)
although it seems that the wireless adapter is installed (claimed) correctly, I'm unable to discover all wireless network in range, it only discovers a few.

i even tried to search for any documentation of bcm43142 over linux wireless wiki. surprisingly, there was only one record, which says "unsupported".
can it be that the driver, which i am currently using, is detecting only 802.11n, and neither 802.11a/b/g?

2 Answers
2

Problems concerning Broadcom wireless cards not being recognized, panicing the kernel and other compatibility issues, happends on a regular basis. The source may be the Broadcom's package/driver called 'bcmwl-kernel-source', which is automaticaly installed by Ubuntu. Check out what I've written at the link below, and also at the links pointed by it, to see if the case described is the same you're experiencing.

firstly, thank you for answering. i am familiar with the packages that you're offering to install, though firmware-b43-installer does not hold the desired driver, and linux-firmware-nonfree is even worse as far as i know, it holds mostly tv cards drivers. and it is not that the wireless is not detected, it does not discover all wireless network in range.
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MrRothMar 3 '14 at 21:30

and a small recommendation, do not copy-and-paste your answers, just give a reference (link) to it.
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MrRothMar 3 '14 at 21:35

MrRoth. Sorry if it wasn't your case. The 'linux-firmware-nonfree' package is also for some wireless cards, like mine's. Firmware bugs can cause different and unexpected behavioral anomalies. I didn't copy-and-paste the answer properly, but a small introduction to contextualize the reader ahead the link.
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Felipe G. MaiaMar 5 '14 at 1:55